Abstract

Rates of obesity are increasing and 640 million adults were considered obese in 2014 an increase of 27.5% over the past three decades. Obesity is strongly linked with increased cancer risk and particularly so for liver cancer in men. Although virus infection had been the leading cause of hepatocellular carcinoma (HCC) in the past, the incidence of obesity induced Non-Alcoholic Fatty Liver Disease (NAFLD) a precursor to HCC is increasing and the number of new HCC cases increased 38% and HCC deaths 56% in the last decade. In this study, we conducted meta-analysis of gene expression profiles obtained from livers of high fat diet fed and chemically induced liver cancers of male C57BL/6 mice in order to elucidate the characteristics of fatty liver and HCC. Three separate studies fed mice high fat diets with 60% kcal% fat (from lard and soy bean oil) diet starting at 7 or 8 week old, and continued for 7-10 weeks (7 weeks, GSE40638; 10 weeks, GSE52333; and 8 weeks, GSE79434). We compared these three studies with a liver cancer study (GSE51188) which induced cancers following a single dose of 25 mg/kg diethyl nitrosamine. Affymetrix Mouse Gene 1.0 ST Array was used for high fat diet studies, and Illumina MouseRef-8 x2.0 BeadChips was used for cancer study. We analyzed each study data with GEO2R (comparison against respective normal liver) and performed meta-analysis of the four data sets by Advaita Pathway Guide software. The analysis identified 118 genes ≥0.2 log2 fold-change (Log2FC) and <0.05 p-value (Allowed >0.05 for 1/3 high fat diet studies to increase the candidate genes, but the direction of changes is the same with other two studies). Among these 118 genes, 22 genes were up-regulated and another 17 genes were down-regulated in all four data sets. 29 genes were elevated in tumor, but lowered in high fat diet. On the other hand, 50 genes were lowered in tumor and elevated in high fat diet. We identified Annexin A2 (Anxa2) among the 22 genes which were up-regulated in all data sets, Anxa2 has consistently been reported to be increased in liver tumors and is associated with poor prognosis. The Anxa2 finding suggests our methodology is robust. Besides Anxa2, Nucleoporin 62 (Nup62), Lactate Dehydrogenase A (Ldha), Oxysterol Binding Protein-Like 3 (Osbpl3) were also up-regulated in all studies (Log2FC of liver tumor: Anxa2=2.75, Nup62=0.35, Ldha=0.53, Osbpl3=1.82). Osbpl3 had higher Log2FC value following Anxa2, and its expression was found to be upregulated in some cancers. Importantly, all these were significantly associated with lower overall survival rates in male HCC patients of The Cancer Genome Atlas (TCGA Genes; ANXA2, p=0.00032; NUP62, p=0.000003; LDHA, p=0.0154; OSBPL3, p=0.0255). This data analysis identified several new genes that may be involved in developing cancer from fatty liver, and they might be useful cancer biomarkers based on their association with poor survival.